I. Field of the Invention
This invention is directed to a polymer-coated support and its use as sand pack in enhanced oil recovery. The polymer is deposited on the support in situ by polymerizing a suitable monomer or monomers on the surface of the support containing a suitable polymerization catalyst deposited thereon.
II. Description of Related Art
One of the problems encountered in thermally-enhanced oil recovery operations is well degradation due to sand abrasion within the well caused by the co-production of the formation sand along with the oil. This is particularly troublesome in formations which consist of very fine, unconsolidated sand. A technique often used to protect the well from sand abrasion involves the introduction of a protective sand pack near the production zone by sequentially injecting graded sand and gravel to create a filtration medium which prevents the formation sand from entering the production well. The injected sand has a gradually increasing particle size, so that the finest sand is injected initially to be maintained at the bottom of the well, and the coarsest sand is injected last, to be maintained at the top of the sand pack. Unfortunately, in enhanced oil recovery processes, such as thermally-enhanced production, at the typical depth of 1000 feet at the corresponding high pressures and the temperatures of about 350.degree. C. or higher, and at the alkaline conditions inherently existing in the formations, the protective sand of the sand pack slowly dissolves, the protective pack is lost and the well integrity deteriorates. As a result, the sand of the sand pack tends to break down into smaller particles and is co-produced with the oil.
To alleviate this problem, it has been proposed in the past to coat the sand with conventional polymers, such as polyethylene. However, polyethylene does not provide a stable coating at the temperatures encountered in thermally-enhanced oil production since such temperatures are higher than the melting point of polyethylene polymers and the temperature threshold of thermal stability of the polymers. Accordingly, polyethylene cannot be used to effectively protect the sand pack from corroding under the harsh conditions of the underground formation.
It is a primary object of the present invention to provide a hydrolytically- and thermally-stable material which can be used to protect a sand pack from the high temperature, pressure and alkalinity conditions inherently existing in underground formations.
Additional objects of the invention will become apparent to those skilled in the art from the following discussion thereof.